The present invention relates to a printing apparatus and method which performs a print operation by scanning a print head having a plurality of printing elements in a direction perpendicular to the convey direction of a recording medium.
A conventional ink-jet printing apparatus is an apparatus for printing an image by discharging an ink. According to this printing scheme, a print head having a plurality of nozzles arranged at a predetermined width along the convey direction of a recording medium is scanned in a direction perpendicular to the nozzle array (this direction will be referred to as the main scanning direction hereinafter), while the recording medium is conveyed in a direction perpendicular to the main scanning direction (this direction will be referred to as the sub-scanning direction hereinafter), thereby printing an image on the recording medium. This ink discharging scheme using a print head includes a scheme of using energy generated by driving the heaters arranged in the nozzles and a scheme of using contraction of the piezoelectric elements arranged in the nozzles.
In either scheme, when all the nozzles arranged on a print head are simultaneously driven, an ink cannot be accurately discharged from the respective nozzles because of crosstalk and the like between the nozzles, resulting in a deterioration in print quality. In addition, since a large current must be temporarily supplied, a large-capacity power supply is required.
In order to solve such a problem, all the nozzles arranged on the print head are divided into blocks each including several nozzles, and the nozzles are driven to perform a print operation at different timings at which an ink is discharged from the respective blocks, thereby maintaining high print quality and suppressing the capacity of the power supply.
Assume that in the above method, an ink is sequentially discharged from groups of eight nozzles of a nozzle array N arranged on a print head IJH, starting from an end of the nozzle array N, at different discharge timings to perform a print operation. When a vertical ruled line, indicated by the solid line in FIG. 1A, is printed by the print width (the first line in FIG. 1A) of the print head IJH, the vertical ruled line is inclined at a predetermined angle (.theta.). In addition, the second line (the vertical ruled line indicated by the dotted line in FIG. 1A and printed by the print head IJH), as a vertical ruled line, printed by a scanning operation following the scanning operation for the first line is inclined. Furthermore, the first and second lines as the vertical ruled lines become discontinuous.
For this reason, as shown in FIG. 1B, the print head IJH is mounted such that the nozzle array N of the print head IJH is inclined toward the sub-scanning direction by the inclination angle .theta. of each line printed as a ruled line as shown in FIG. 1A, thereby correcting each ruled line printed as a line to be vertical.
Assume that a print head is mounted such that the nozzle array is inclined toward the sub-scanning direction by the angle .theta.. Even in this case, if the print head is of a replaceable type that is detachably mounted on a printing apparatus, the angle .theta. slightly deviates when the print head is mounted. As a result, vertical ruled lines are inclined, and the print quality deteriorates.
As shown in FIG. 2, a deterioration in print quality, e.g., color misregistration or a ruled line offset, occurs unless print heads IJH(Y), IJH(M), IJH(C), and IJH(K) for the respective colors, i.e., yellow, magenta, cyan, and black are accurately mounted at angles .theta.1, .theta.2, .theta.3, and .theta.4 in the main scanning direction and the sub-scanning direction as in an integral color head. Furthermore, it is more difficult to improve the mounting precision associated with the angle .theta. than to mount each print head in the main scanning direction and the sub-scanning direction, resulting in an increase in cost.